1. Field of the Invention
This invention relates to a disk film projector, and more particularly, to a disk film projector which reproduces an image recorded on a rotary disk of film into a visual image.
2. Description of the Prior Art
There is known in the art a photosensitive film in the form of a rotary disk, or a so-called disk film, on which still images are to be recorded.
Recorded images on a disk film may be reproduced in the form of a hard copy or print. There is also a remarkable demand for obtaining a soft copy from a disk film for use. Because of the smaller size of a frame of the disk film, it is necessary to reproduce a frame of the image in the form of a soft copy which is enlarged to a size suitable for use. Negative images recorded on the negative type of disk film must be reversed into positive images.
These demands may advantageously be satisfied with a technique by which frames of a disk film are shot with a television camera to produce video signals representative thereof, which are in turn used for image reproduction on an image display device such as a CRT, and/or recordation on a recording medium such as a magnetic tape, magnetic disk, as the case may be.
For shooting desired one of the frames of a disk film by a television camera, the disk is loaded in a projector to be rotated for setting the desired using frame to the projecting position thereof. For practical purposes, the disk may advantageously be rotated both manually and by electrical driving means for the disk film.
Frames are recorded along the circumference of the disk film. In order to random access to a desired frame, manual operation may give rise considerable reduction in access time than electrical driving means for incrementally advancing a frame at a time. In a customary disk film, the number of a frame is indicated in a margin of the film between the adjoining frames. Therefore, a desired frame may be retrieved by rotating the disk slowly in manual operation to bring a frame number indication associated therewith at the projecting position for visually checking the indication.
On the other hand, electrical driving may preferably be applicable to consecutive shooting of a large number of frames, synchronized stepping of the disk frames with voice reproduction, or controlling incremental advancement of frames from a remote position. It is therefore required that the projector be designed to cause a disk film to rotate in response to both manual and electrical movements.
For satisfying the demand, both electric motor and manual rotating elements are operatively linked with a driving shaft causing the rotation of the disk film. In general, in order to design an apparatus reduced in size, a small-sized electric motor capable of producing a higher r.p.m. is used to produce a high driving torque in conjunction with an associated driving mechanism having a higher gear ratio. When a motor drive mechanism including such a small-sized electric motor and a driving mechanism of higher gear ratio is driven as an external load, however, it works as a heavy load of torque. With a system in which the electric motor is perpetually interconnected with the manual driving mechanism by the driving shaft, therefore, the motor will act as a heavy load when the manual driving mechanism is operated manually. It is therefore difficult to accomplish a rapid random access to a desired frame of the disk.
Moreover, in a system in which the electric motor is linked directly to the driving shaft, the accuracy in adequately positioning a desired frame at the projecting station is accomplished only by providing an electric motor presenting high positioning accuracy, or a special positioning device in the driving system.